The past decade or so has seen a lot of developments in the action genre, from dual-stick controls to closely spaced checkpoints to voice acting in cutscenes. No one has been very successful, however, in bringing these innovations to the classic, top-down, multidirectional shoot-'em-up genre, a situation that Aqua, a $10 XBLA title, hopes to rectify.

At its best, Aqua is a lot of fun. With a lot of shooting and a little bit of strategy, players blast their way through a few hours' worth of water-based action, much the way they'd shoot through a modern first- or third-person shooter. But thanks to some gameplay and technical problems, some serious and some merely annoying, Aqua is not the Gears of War of the top-down "shmup."

The basic setup here does a good job of infusing the genre with a modern flavor. You move and shoot using the two-joystick setup that Geometry Wars popularized, fire torpedoes and lay mines with the trigger buttons, and activate your speed boost, switch weapons, and call in air support with the face buttons. Between missions, you can outfit your ship with different weapon types that you've unlocked, or even change ships entirely. The weapons include flamethrowers, Gatling guns, shotguns, and machine guns, and the ships vary in speed (with the faster boats unable to carry the more powerful weapons). All this makes for deeper gameplay than most arcade classics provided, but it's remarkably intuitive to learn.

Since Aqua is set on the water, as the name would imply, the levels aren't particularly intricate, but they do allow you to roam the high seas and navigate various rivers, hunting down bad guys, infiltrating enemy compounds, and exploring.

The missions here are nothing special, either: protect this base from waves of enemy attacks, escort that ship from point A to point B, and fight your way through hostile territory. Nonetheless, the game never loses sight of its purpose in life, which is to let you mow down different types of baddies at a rapid pace. You don't pause to think about originality when you're dealing out copious amounts of death.

There are some squad-based missions, and you can have your compatriots follow you, attack the enemy, or protect allied bases and ships. There's even some very basic stealth. This adds a thin layer of strategy on top of all the shooting, which is a nice distraction and doesn't detract from the core gameplay. A deeper game would do more with this, but we're fine with it the way it is.

The biggest problem with the gameplay is that the difficulty isn't particularly well-balanced. Even on the medium setting we found the first major boss to be virtually unbeatable. That is, until we figured out what seems to be a glitch in the programming: If you drive away from him at an angle and keep him barely on the screen, he won't shoot at you often but you can shoot him. Later in the game, there are some major problems with the spacing of the checkpoints, which can result in some thrown controllers. There's nothing more obnoxious than finally finishing that long stretch of fighting you were having problems with, only to realize there's another stretch to go before you can die without starting all over.

The steampunk-influenced presentation here isn't bad, for the most part. The in-game graphics aren't jawdropping, and we would have liked to have seen some more realistic-looking fire and explosions, but the visuals get the job done. Similarly, the sound effects could have a little more punch, and don't even get us started on the voice acting; when you're busy taking out waves of bad guys, you won't focus much on the bells and whistles.